Metais pesados em plantas de milho cultivadas em latossolos repetidamente tratados com biossólido

Abstract

The presence of heavy metals in sewage sludge amended soils can cause concern due to the possibility of the absorption of these metals by plants growing on these soils. The availability of Cd, Cr, Cu, Ni, Pb and Zn to corn plants in soils continuously treated with biosolids (sewage sludge) was evaluated by an experiment performed in 0.5 m3 pots with a dystrophic Typic Hapludox (LAd) and a dystrophic Rhodic Hapludox (LVd). The adopted statistical design was random blocks with four treatments (LAd+sludge, LAd, LVd+sludge and LVd) and four replications. Biosolids from SABESP-Barueri treatment plant (São Paulo/Brazil) were applied every two months to the soils until one year before planting corn, totallizing 388 Mg ha-1. Before sowing the corn the control treatments (without sludge addition) received lime and NPK fertilizers. During crop growth soils with biosolids were also fertilized with NPK. At harvest corn plantlets were divided into: diagnose leaf, old leaves, stem, sheath, grains, corn cob and straw. This material was submitted to nitro-percloric digestion, and metals were quantified by conventional flame atomic absorption spectrophotometry. The successive biosolid applications, at rates of 78 Mg ha-1 each, did not increase corn yield, however plant availability was observed for Cu and Zn. No plant availabilities for Cd, Cr, Mn, Ni and Pb were observed.